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The challenges of effective surveillance in the event
of a food incident Junshi Chen
Institute of Nutrition and Food Safety, Chinese Centre for Disease Control
and Prevention
Outline
o International food surveillance systems/programmes;
o food surveillance systems/programmes in China;
o Case analysis of effective surveillance in the event of a food incident – the melamine crisis.
WHO Global Foodborne Infections Network (GFN) o Mandate – to enhance the capacity and quality
of foodborne pathogen isolation, identification, serotyping, and antimicrobial resistance testing throughout the world and support local interventions that reduce the human health burden of foodborne diseases.
o Key focus – to improve participants' skills in the development of foodborne disease surveillance and outbreak investigation.
WHO Outbreak investigation and response o Foodborne outbreaks of international public
health significance are identified through WHO's Alert and Response Operations Team (INFOSAN) through notification through members of the Global Foodborne Infections Network (GFN) and other networks such as EnterNet.
o An outbreak investigation manual is being drafted.
WHO GEMS/FOOD Programme o Global Environment Monitoring System – Food
Contamination Monitoring and Assessment Programme, since 1976.
o Data collection for hazard occurrence, food composition and food consumption.
o Training and capacity building at national/regional level of chemical exposure assessment based on Total Diet Studies.
o Development and dissemination of guidelines and recommendations for exposure assessment methodologies.
Outline
o International food surveillance systems/programmes;
o food surveillance systems/programmes in China;
o Case analysis of effective surveillance in the event of a food incident – the melamine crisis.
Food Safety Law of China (effective from June 1, 2009)
Article 11 A surveillance system for food safety shall be established nationwide for surveillance over food-borne disease, food contamination and other food-related hazards to human health. The health administrative departments of the State Council shall establish and implement plans for the surveillance of national food safety in conjunction with other departments of the State Council.
National food safety surveillance system in China
Before 2009
Ø 17 provinces included in chemical hazards monitoring (yellowgreen +red)
Ø 22 provinces involved in
microbial hazards monitoring and foodborne illness reporting system (yellowgreen + blue)
From 2010
all provinces join the
national food monitoring program
Examples of surveillance findings (1)
o Pilot started in 7 provinces in 2010.
o 17 sentinel sites – 103 hospitals, cases with laboratory diagnosis of Salmonella, V. parahemolyticus or Shigella.
o 23 surveillance site (around 0.5 million population) – monthly household visit to identify cases of acute gastro-intestinal disease.
Active surveillance on foodborne illness occurrence
Examples of surveillance findings (2) Hexachlorocyclohexane in aquatic products – tracking the source of contamination
HCH residue in TDS
0
20
40
60
80
South1 South2 North1 North2
TubersBeansMeatsEggsFishVegetablesFruitsDairyGrains
mg/kg
Various HCH isomers in aquatic foods in the 4 regional baskets
0
20
40
60
80
South1 South2 North1 North2
mg/kg
a-HCH g-HCH b-HCH
g-HCH in aquatic food samples from various provinces
0
100
200
300
400
Hubei Guangxi Sichuan
mg/kg
0
100
200
300
400
Heilongjiang Liaoning Hebei
mg/kg
South 2 North 1
g-HCH concentrations in individual aquatic food samples
0
100
200
300
400
500
600
Hubei Heilongjiang
Sea Fish River FishRiver shrimp
mg/kg
Outline
o International food surveillance systems/programmes;
o food surveillance systems/programmes in China;
o Case analysis of effective surveillance in the event of a food incident – the 2008 melamine crisis in China.
o From 21 September to 27 November, 22,380,000 (22 million) children were checked for urinary tract damage and 294,000 cases of abnormal urinary tract were found.
o 51,900 cases were hospitalized and 861 cases are still in the hospital.
o Retrospective survey found 11 death cases. Among them, 6 were caused by renal failure caused by melamine-tainted infant formula and other 5 died of other renal diseases.
MOH News Release (1 December, 2008)
o High concentrations of melamine were found in Sanlu infant formula samples collected from the home of the affected cases;
o Very high level of melamine was found in raw materials used for milk adulteration;
o Melamine is the major component of the stone collected from the urine of affected cases.
Melamine contaminated infant formula is the Cause
Melamine contents in 111 Sanlu infant formula samples (mg/kg)
Source: China CDC
Melamine No. Samples Mean Median P70 P90
<0.05 24 - - - -
0.05-1000 32 506 555 652 900
1000-1900 22 1,439 1,500 1,700 1,840
1900-2600 22 2,212 2,200 2,300 2,560
>2600 11 3,453 3,000 4,000 4,500
Melamine content in Sanlu and non-Sanlu infant formula samples, Gansu Province
Source: China CDC
Brand No. Samples Mean (mg/kg)
Median (mg/kg)
P90 (mg/kg)
Sanlu 52 1,674 1,700 2,880
Non-Sanlu 38 4.06 0.01 8.80
Melamine and its analogs in Sanlu infant formula samples, Gansu province (N=52)
Source: China CDC
Mean (mg/kg)
Median (mg/kg)
P90 (mg/kg)
Melamine 1,673.6 1,700.0 2,880.0
Cyanuric acid 1.6 1.1 3.4
Ammeline 1.7 1.3 4.3
Ammelide 2.9 2.1 8.1
Maximum consumption level of infant formula in infants and young children
Source: China CDC
Age (mos.)
Mean BW (kg)
Maximum consumption (g/day)
3 5.5 129
6 7.0 150
12 10.0 150
24 14.0 120
Melamine concentrations (mg/kg) in Sanlu infant formula samples
Source: China CDC
Notes: Sample A: all samples; Sample B: samples collected from affected area in Gansu province. LOQ 0.05 mg/kg.
No. Samples Mean Median P90 Maximum
A 111 1,212 1,000 2,600 4,700
B 52 1,674 1,700 2,880 4,700
Intake estimates of melamine from Sanlu infant formula (N=111)
Source: China CDC
Age (mos.)
Melamine intake (mg/kg bw)
Mean Median P90 Maximum
3 28.4 23.4 61.0 110.2
6 26.0 21.4 55.7 100.7
12 18.2 15.0 39.0 70.5
24 10.4 8.6 22.3 40.3
o Data from the 2008 Chinese incident illustrate that infant formula contaminated mainly with melamine can result in stone formation if sufficient melamine is present.
o Data indicate that stones are composed of uric acid and melamine at a molar ratio ranging from 1.2:1 to 2.1:1, without evidence of the presence of cyanuric acid or other melamine analogues.
o Most children with stones did not have clinical signs of illness. However, in severe cases of renal failure and/or blockage, clinical signs did occur.
Risk characterization and Epidemiology
o The dietary exposure to Sanlu infant formula in China at the median levels of melamine ranged from 8.6 to 23.4 mg/kg bw/day. This is about 40
- 120 times the TDI, which explains the dramatic health outcome in Chinese infants.
o Estimates of potential exposure of adults to melamine from foods containing adulterated milk products were 0.8–3.5 times the TDI.
o Estimates of exposure to baseline levels of melamine from all sources (up to 13 µg/kg bw) were well below the TDI.
Risk characterization
o Many countries have introduced control limits for melamine in infant formula and other foods.
o Limits for melamine in powdered infant formula (1 mg/kg) and in other foods (2.5 mg/kg) would provide a sufficient margin of safety for dietary exposure relative to the TDI.
o To develop international MRLs for melamine in infant formula and other foods was agreed at the 2009 Codex Committee on Contaminants in Foods (CCCF).
Risk management
Conclusions o National food safety surveillance systems are
essential for identifying/early warning of potential food incident.
o Target surveillance programme could provide necessary scientific data to guide food incidence management.
o However, qualified laboratory facilities, well trained personnel and well established mechanisms of inter-sectorial collaboration are the main challenges for most developing countries to build up effective national surveillance capability.